1. Field of the Invention
This invention relates to a mirror array with an adjustable focus. A preferred embodiment of the invention is in the field of solar energy collection. Such devices are commonly called heliostats, and often—as in this case—can adjust throughout the year, according to the season. Furthermore, many heliostats track the sun daily from east to west
2. Description of Related Art
The prior art contains many examples of adjustable mirror arrays, many of which are primarily or exclusively designed as solar collectors. These heliostats employ a great variety of methods to attain the goal of focusing sunlight on a common point. Some of these heliostat arrays contain many individually controlled mirrors, such as U.S. Pat. Nos. 4,122,827 and 7,192,146. Other arrays, including U.S. Pat. Nos. 4,102,326, 4,425,904, 4,466,423, and 4,832,002 contain mirrors that are linked together mechanically, but with cables or belts. The arrangement of cables requires, however, that each mirror moves the same amount under a single input, but the present invention moves each mirror a different amount in order to preserve the parabolic geometry of the reflector array. Furthermore, it is believed that cables may pose a liability, as they can break. Related U.S. Pat. Nos. 4,110,010, 7,677,241 and 7,905,227, are mechanically linked with configurations that appear more robust than the arrays using cables.
U.S. Pat. No. 6,349,718 looks similar in some respects to the present invention, but is actually substantially different, particularly regarding the movement of the mirrors. It appears that they can be independent or linked together, but if linked, they are to be forced to move the same amount.